It is a very good practice, if not an outright requirement, to have a second online copy of a PostgreSQL server in high availability clusters. Without such an online server, recovery from an outage may require hours of incidence response, backup recovery, and server provisioning. We have everything to gain by having extra online servers.
In addition, the process of setting up a hot standby acts as the basis for creating PostgreSQL streaming replicas. This means that we can reuse this recipe over and over again anytime we need to create PostgreSQL mirrors, provision extra backup copies, set up test instances, and so on.
All of this is made possible by the pg_basebackup command.
A hot standby server should have similar, if not exactly the same, specifications as the PostgreSQL server it is subscribed to. Try to accomplish this if possible. Also refer to the previous Securing the WAL stream recipe, as we will be consuming WAL files in this recipe.